752 SUMMARY OF CURRENT EESEAR0HE8 RELATING TO 



varieties of it. Thus cells of Chara and Elodea, altliougli dis- 

 solving in nitrite of amnaonia, are not altered by Bacillus amylo- 

 hacter. 



Generally this microscopical agent does not aflfect starch, which 

 is a lower polymere than cellulose. Nevertheless, Van Tieghem has 

 found that in certain plants, contrary to what usually takes place, 

 this microbe subjects the grains of starch to butyric fermentation, 

 without destroying, or before destroying, the walls of the cells into 

 which it has penetrated. This is the case with the root of Adoxa 

 mcschatellina* 



It is easy, with a high magnifying power, to study, under the 

 Microscope, the course of the butyric fermentation. It is only 

 necessary to guard against the preparation drying up and coming in 

 contact with the air, which is fatal to Bacillus amylohacier. 



Crystals of Carbonate of Lime. — In the condition of cystoliths, or of 

 very small granular crystals, carbonate of lime is not rare in the pro- 

 toplasm or sei:)ta of the cells (for example, plasmodia of the Physarese, 

 epidermal cells of several Urticacene, cell-walls of CoralUna and 

 Acetahularia). Acids, and particularly hydrochloric acid, dissolve it 

 by disengaging, under the form of bubbles, the carbonic acid which it 

 contains. This disengagement, easily observed under the Microscope, 

 is very characteristic. 



Crystals of Oxalate of Lime. — These crystals, which are much more 

 frequent than the former, are distinguished from them chemically by 

 being insoluble in acetic acid, and soluble, without disengagement of 

 gas, in hydrochloric acid. 



It is useful to apply these reactions in the case of crystals of the 

 quadratic system with six equivalents of water. But for the raphides 

 of the monoclinic system, with two equivalents of water, they are 

 almost always superfluous, their form being sufficient to reveal their 

 nature. 



VI. COLOUEING. " . 



1. Albuminoid substances. 



Protoplasm. — It has been believed for a long time that the chemical 

 reactions of living protoplasm are essentially different from those of 

 dead protoplasm.f In 1874 Sachs wrote : " Solutions of different 

 colouring matters, as aqueous solutions of the colours of flowers and 

 the juices of fruits, esjpecially also weak acetic solution of carmine, 

 have no power of colouring living protoplasm ; but if it has been 

 previously killed, or if it has lost its vital properties by long- 

 continued action of these reagents, it absorbs a relatively larger 

 quantity of colouring material than of the solvent, and the whole 

 substance assumes a much more intense colour than the reagent. 

 Solutions of iodine in water, alcohol, potassium iodide, or glycerin, 

 act in a similar manner ; they all cause a yellow or brown colouring 



* Van Tieghem, " Anatomie de la Moscliatelline," Bull. Soc. Bot., ii. (1880) 

 p. 282. 



t Sachs, ' Text-book of Botany,' 2nd edition, p. 37. 



